1. Field
The disclosure relates to a method, system, and article of manufacture for the propagation by a controller of reservation made by a host for remote storage.
2. Background
Certain information systems provide high availability for data by implementing clusters of servers. The servers in a cluster may share data storage resources, such as disks. In case of a failure of a server in a cluster, one of the operational servers can take control of the storage resources and service requests. In certain other information systems, storage controllers may provide data replication services, such as, point-in-time copy and synchronous or asynchronous controller-to-controller (remote) copy. In such systems, data can be replicated from a primary controller to a remote or secondary controller that may be hundreds of kilometers away from the primary controller, by using remote copy. Such solutions may protect the data from a disaster that affects the primary site while not necessarily ensuring continuous availability of data. In certain other information systems, data is continuously replicated from the primary to the secondary site to ensure continuous availability of data.
Certain systems may use Small Computer Systems Interface (SCSI) reservation commands to claim ownership of a disk to provide continuous availability of data. For example, when a cluster initially starts up, a first node may put a reservation on a quorum disk and the first node may become the owner of the disk. Nodes that join the cluster at a later point in time do not attempt to claim the quorum disk until the nodes that join are unable to communicate with the current quorum owner node. Since all servers in the cluster physically share the disk resources including the quorum disk, the cluster servers may have to be near each other. In case of a disaster that affects the region in which the cluster servers reside, a complete loss of data may occur. Certain other systems may also use SCSI reservation commands to manage or change remote copy states in a distributed environment with geographically separated nodes for ensuring continuous availability of data.